# Full text of "Text Book Of Mechanical Engineering"

## See other formats

Appendix V.

which means that if Tm be satisfied the shaft will be 4*57" dia.; but
such a shaft would be too springy, for                                              *

~     -2/1       2x9000x240          .

g = ^ =   - — *__ - :±_ = -0647
Ca      13,000,000x5*15

or = -0647 x 57'4 = 37 degrees.

Hence 4*57 does not satisfy stiffness. We also learn that a shaft
I9"dia. is sufficiently stiff when stressed to 9000 Ibs. per sq. in., but
too stiff in fact, because our Tm cannot cause so high a stress, for

^     Tmxi6      171,000x16x7

— ---- __ = —> - L — I27 ibs. per sci. in.

7T (t*       I9XI9XI9X22                  ^       *

We conclude that the proper course is to directly connect Tni with
stiffness, for we shall not then exceed the required torsion angle ; but
the maximum stress will be much under 9000 Ibs., which yet satisfies
the conditions.

2/^                      J    JT       * 6   Tm

.    ^4 ^   2X16X17^,000X240X57-4X7   =   ig
22 X I3,OOO,OOO

and d = 6'48//
Also the stress produced by T,n will be

-     i6Tm     16x171,000x7             .,

/=   TO* -      22x6-48^      = 3^0 Ibs. per sq.an.

Answer: — ^4 x/f^/? 6*48" dia. will sustain a Tm of 171,000 /6s.
without deflecting mare than i° in 20 ft. of length, the maximum stress
not exceeding 3220 Ibs. per sq. in.; and the lower diagram in Fig. 917
will assist in shewing the peculiar conditions of the problem.

CHAPTER X.

Pp. 709 and pjrj. Petrol-driven Motor Cars.—There
are now three practical sources of power for motor cars :
steam, electricity, and oil or spirit. Steam has found favour on
account of the highly regulable character of the working gas, the
dispensing with spur changing gear and its noise and shock, and
the reduced cost of repairs through freedom from vibration. On